This invention relates to fast recovery diodes and more specifically relates to a single mask process for the manufacture of a fast recovery diode with an increased Schottky diode area with a trench topology.
The manufacture of fast recovery diodes with trench topology now requires the use of plural mask steps and have a relatively small Schottky diode area relative to the die or chip area.
It would be desirable to provide a fast recovery diode having an enlarged Schottky area for a lower forward voltage drop and to make the device with a reduced number of masks steps, preferably a single critical step.
In accordance with the invention a novel fast recovery diode is made with a single critical mask step which defines a trench etch region. A locos-type process is also employed to enable the selective removal of nitride in the active area before metallization. In the resulting device, the bottoms of the trenches receive a local P type diffusion, producing small P-N junctions at each trench, while the full trench walls and the mesas between trenches receive a Schottky-forming metal.